It has become increasingly important to accurately space insulated multiple bands of conductors with respect to each other and laminated flat ribbon cable has increasingly come into use for this purpose. Precise control of electrical characteristics such as impedance, capacitance, cross talk and attentuation, especially important in digital data, and signal, transmission may be thereby achieved. Both controlled regular spacing and controlled irregular spacing, of multiple conductors in ribbon cable form has been achieved, in the prior art, by laminating the accurately spaced insulated (or uninsulated) multiple conductors between thin plastic film, such as 5 mil polyvinyl chloride (pvc) film or 5 mil Teflon* film. FNT *Teflon is a registered trademark of E. I. duPont de Nemours, Wilmington, Delaware.
Multiple pairs of insulated conductors have also been accurately laterally spaced, in ribbon cable, by laminating multiple pairs of insulated twisted conductor pairs between thin plastic sheet or film, the twisted pairs being first laid onto a first plastic film and encapsulated and accurately oriented by a second plastic film laminated to the first film. The use of twisted pairs of multi-conductor cable is of great importance in the field of communications, data processing and other applications where cross-talk in signal transmission must be kept to a minimum. The laminated, twisted pair, multi-conductor ribbon cable of the prior art has, however, one material drawback, namely that present, standard, terminating techniques require that after the twisted pairs which are to be terminated have been separated from the laminate, the ends of each pair must then be untwisted manually, or with the aid of a special pliers or other tools. The separation procedure is time consuming and becomes impractical when dealing with large amounts of termination points or when it may be preferred to terminate the ends of such multi-conductor laminated ribbon cable onto an Insulation Displacement Connector (IDC) or other mass termination device; for an IDC or the like requires great accuracy in the spacing of the ends of the multi-conductor cable which are to be mass-terminated thereon.
The invention is therefore directed towards a method and apparatus for making improved laminated multi-conductor ribbon cable, having a plurality of twisted insulated conductor pairs in combination with intermittent straight sections laminated therein at precise lateral spacings which overcomes the just-mentioned time-consuming problem of untwisting the cable for termination purposes, while at the same time, more precisely orienting the termination points of the conductors for connection to IDC connectors, and the like.
The applicant is aware of U.S. Pat. No. 3,579,823 entitled "APPARATUS AND METHOD FOR APPLYING INDEXING STRIPS TO CABLE PAIR GROUPS" and issued to T. J. Gressit on May 25, 1971. This patent relates to a method and apparatus for the manufacture of multi-pairs of twisted cable. The twisted multi-pairs have compliant plastic strips placed at periodic straightened intervals in the twisted pairs for the purpose of maintaining the lateral spacing, at the straight intervals, between the conductor pairs.
It is a major object of this invention, however, to more positively achieve a precise, lateral spacing of both twisted pair portions and the intermittent straight conductor portions of the multi-conductor cable pairs, so that mass termination of the straight portions can be reliably achieved, as well as realizing other processing advantages. The method and apparatus, by which this may be accomplished, is set forth herein.